Whow, this is quite strange, what I usually use (haven't tried it on
NetBSD with CentOS because I use Debian most of the time, but I think
it should work).
Download files from
http://mirror.centos.org/centos/6.2/os/x86_64/images/pxeboot/
Sample config file:
kernel = "/path/to/vmlinuz"
ramdisk = "/path/to/initrd.img"
name = "my_centos_domu"
memory = 512
vcpus = 1
vif = ['bridge=my_bridge']
disk = ['file:/path/to/my/img,xvda,w']
After that:
xm create -c /path/to/config

Once the system is installed, remove kernel and ramdisk options and
add:

bootloader = "pygrub"
That should do it (I think). Your config file looked like a mess
between a HVM and a PV domain.
Regards, Roger.

Re,

It's better but not completly full (i would be more patient after a few
seconds the boot process begin).

The install process begin
The retreive of the install.img file it's OK.

But i always have error on the storage file (linux.img created with
DD), during the install process i have somme message tha tell me to
initialise the DD because there is somme error.